John is traveling north at 20 meters/second and his friend betty is traveling south at 20 meters/second. if north is the positive direction, what are john and betty's speeds? -20 meters/second, 20 meters/second 20 meters/second, 20 meters/second -20 meters/second, -20 meters/second 0 meters/second, 40 meters/second done

20 meters/second -20 meters/second

Explanation:

John is travelling north at 20 meters/second. If north is the positive direction, then John is travelling at +20 meters/second, or just 20 m/s.

Betty is travelling south at 20 meters/second, then she is travelling in the negative direction, making her speed -20 meters/second.

air exerts forces on falling objects near earth’s surface.

explanation:

the term 'free falls' refer to object that are falling towards the earth, in a situation in which gravity is the only force acting on the object.

for an object in free fall, the acceleration is constant (g, the gravitational acceleration), and so the velocity of the object constantly increases.

for objects near earth's surface, there is always another force acting on the object: the resistance due to the air. this force is opposed to the direction of fall of the object, and it is proportional to the velocity of the object, so as the object falls down, this force increases up to a point when it balances the force of gravity, and the object continues its motion at constant velocity (called terminal velocity). since in this case gravity is not the only force acting on the object, we are not in a situation of free fall.

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